This application claims the priority of German application 198 37 182.9 filed in Germany of Aug. 17, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a transport belt for transporting a fiber strand to be condensed through a condensing zone, comprising a perforation for an air suction stream which suctions the fiber strand.
A transport of this type is known from the U.S. Pat. No. 5,600,872 as prior art. It is produced in the way of drafting aprons of spinning machines whereby for the purpose of suctioning the fiber strand, holes are arranged in one row in a fiber strand transport direction. The diameter of these holes corresponds to the width of the fiber strand to be condensed.
It is an object of the present invention to produce a transport belt of the above mentioned type, which is particularly favorably designed with regard to the condensing effect.
This object has been achieved in that in at least one fiber strand carrying area a perforation is present, which comprises at least 100 holes per square centimeter.
Such a large number of holes ensures a very even and thus homogenous air through-flow. It is not the size of the perforation which determines the degree of the condensing effect, but rather a suction slit arranged underneath the transport belt, and over which suction slit the transport belt slides. The finer the perforation, the better the condensing effect. For this reason, there are in further embodiments of the present invention at least 1000 holes per square centimeter provided. In especially preferred embodiments, in at least the area which carries the fiber strand through the condensing zone, the overall percentage of holes should amount to a total cross section of hole openings of at least 40% of the total strand carrying area.
The transport belt consists particularly advantageously of close-perforated woven filaments, in particular monofilaments. As a result of the weave, the perforation occurs so to speak by itself, without the holes having to be stamped out of a previously hole-free transport belt. Furthermore, by means of the degree of fineness of the filaments, the chosen number of holes per surface unit can be as high as is desired. The filaments chosen for the woven material have in addition the advantage that the edges can be reinforced by means of a heating process.
The production of the transport belt according to the present invention is possible in a variety of ways:
In one embodiment according to the present invention, an endless tube is woven, which is subsequently cut to size to fit the desired width of the transport belt. In another embodiment of the present invention, a woven fabric is produced in the desired width of the transport belt and subsequently welded to form an endless belt. It has been shown that the overlapping areas which arise from welding do not in any way impair the quality of the yarn. In a further embodiment it is provided that a belt strip is cut out of a larger surface and that the endless belt is then subsequently produced from this strip by means of welding. In particular in the case of the latter method, it is possible in a simple way to reinforce the lateral edges already during cutting, in that a heated cutting tool is used.
It can be favorable when the transport belt, made from woven filaments, comprises a stiffening skeleton, which can, for example be produced in that rougher filaments are woven in at certain intervals.